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It is the first lecture notes which give an overview of the whole networking system in a top down approach including application layer, transport layer, network layer, link layer.
Typology: Lecture notes
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Instructor: Qian Zhang, http://www.cse.ust.hk/~qianzh/ Lectures: Tue 3:00pm – 4:20pm Thur 3:00pm – 4:20pm Venue: Rm 6573, Lift 29 - 30 Web site: http://course.cs.ust.hk/comp4621/
Lecture notes and tutorial materials Download course materials before class Homework and programming assignment will be put online Tutorial and Lab will start in week #4 (Sept 24/25, 2018) Lab 1 Tue 1 :30pm - 2:20pm Room 4214 (lift 19) Lab 2 Monday 12:00pm - 12:50pm Room 4214 (lift 19)
Bottom Up : Start with physical (e.g., wires) layer and move up to applications (e.g., mail, web browsers) layer explaining how functions are implemented Top Down : Start with Application layer and move down to Physical layer, explaining what expectations from applications, and how such services are implemented Application Transport Network Link Physical Computer Networking: A Top-Down Approach James Kurose and Keith Ross, Pearson (6th^ Ed.)
There are differences between collaborations or discussions and copy! 1 st^ Time: all involved get ZERO marks, and reported to ARR 2 nd^ Time: need to terminate (Fail grade) Midterm or Final exam: an automatic FAIL
Process and thread, DMA and interrupt, inter-process communications
UNIX environment C/C++ programming
Lectures: Lecture notes are available before class It is important to attend the lectures (because not all materials and concepts are covered in slides) Learn from textbook Tutorials Supplement the lectures with more examples Socket programming and project Reading the corresponding materials in the textbook Slides do not cover everything Chapter or sub-chapter summary These will be put online at the end of each chapter
Written assignments Due by time specified Re-grade requests will only be entertained within one week after the homework are handed back Late policy: 15 % reduction, only one day delay is allowed. Programming assignment Individual projects Due by time specified Run on Unix and submit it using CASS Re-grade policy will be announced Late policy : 15 % reduction, only one day delay is allowed.
Introduction (1 weeks) Internet, network edge and core, performance, history Application Layer (2.5 weeks) Web, HTTP, E-mail and SMTP, DNS Peer-to-Peer applications, socket programming Transport Layer (3 weeks) UDP and TCP Principles of congestion control, TCP congestion control Network Layer (3 weeks) Virtual circuit, datagram, router, IP Routing protocols Link Layer and Local Area Network (2.5 weeks) MAC, addressing Ethernet and link-layer switch Introduction
what’s the Internet? what’s a protocol? network edge; hosts, access net, physical media network core: packet/circuit switching, Internet structure performance: loss, delay, throughput security protocol layers, service models history 1 - 14
Introduction
packet switching, circuit switching, network structure
1 - 15 Introduction
millions of connected computing devices: hosts = end systems running network apps communication links fiber, copper, radio, satellite transmission rate: bandwidth Packet switches: forward packets (chunks of data) routers and switches wired links wireless links router mobile network global ISP regional ISP home network institutional network smartphone PC server wireless laptop 1 - 16
Web, VoIP, email, games, e- commerce, social nets, …
hooks that allow sending and receiving app programs to “connect” to Internet provides service options, analogous to postal service mobile network global ISP regional ISP home network institutional network Introduction 1 - 19 Introduction
“what’s the time?” “I have a question” introductions … specific msgs sent … specific actions taken when msgs received, or other events
machines rather than humans all communication activity in Internet governed by protocols
1 - 20
Introduction
Hi Hi Got the time? 2: TCP connection response Get http://www.awl.com/kurose-ross
1 - 21 Introduction
packet switching, circuit switching, network structure
1 - 22
Introduction Access net: digital subscriber line (DSL) central office ISP telephone network DSLAM voice, data transmitted at different frequencies over dedicated line to central office use existing telephone line to central office DSLAM data over DSL phone line goes to Internet voice over DSL phone line goes to telephone net < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) < 24 Mbps downstream transmission rate (typically < 10 Mbps) DSL modem splitter DSL access multiplexer 1 - 25 Introduction Access net: cable network cable modem splitter
cable headend Channels V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O D A T A D A T A C O N T R O L 1 2 3 4 5 6 7 8 9 frequency division multiplexing: different channels transmitted in different frequency bands 1 - 26
Introduction data, TV transmitted at different frequencies over shared cable distribution network cable modem splitter
cable headend CMTS ISP cable modem termination system HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate network of cable, fiber attaches homes to ISP router homes share access network to cable headend unlike DSL, which has dedicated access to central office Access net: cable network 1 - 27 Introduction Access net: home network to/from headend or central office cable or DSL modem router, firewall, NAT wired Ethernet (100 Mbps) wireless access point (54 Mbps) wireless devices often combined in single box 1 - 28
Host: sends packets of data host sending function: takes application message breaks into smaller chunks, known as packets , of length L bits transmits packet into access network at transmission rate R link transmission rate, aka link capacity, aka link bandwidth R: link transmission rate host 21 two packets, L bits each packet transmission delay time needed to transmit L - bit packet into link L (bits) R (bits/sec)
1 - 31 Introduction Physical media bit: propagates between transmitter/receiver pairs physical link: what lies between transmitter & receiver guided media: signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely, e.g., radio twisted pair (TP) two insulated copper wires Category 5: 100 Mbps, 1 Gpbs Ethernet Category 6: 10Gbps 1 - 32
Introduction Physical media: coax, fiber
two concentric copper conductors bidirectional broadband: multiple channels on cable HFC
glass fiber carrying light pulses, each pulse a bit high-speed operation: high-speed point-to-point transmission (e.g., 10’s- 100 ’s Gpbs transmission rate) low error rate: repeaters spaced far apart immune to electromagnetic noise 1 - 33 Introduction Physical media: radio signal carried in electromagnetic spectrum no physical “wire” bidirectional propagation environment effects: reflection obstruction by objects interference
terrestrial microwave e.g. up to 45 Mbps channels LAN (e.g., WiFi) 11Mbps, 54 Mbps wide-area (e.g., cellular) 3G cellular: ~ few Mbps satellite Kbps to 45Mbps channel (or multiple smaller channels) 270 msec end-end delay geosynchronous versus low altitude 1 - 34
Introduction Packet-switching: store-and-forward takes L / R seconds to transmit (push out) L - bit packet into link at R bps store and forward: entire packet must arrive at router before it can be transmitted on next link one-hop numerical example: L = 7.5 Mbits R = 1.5 Mbps one-hop transmission delay = 5 sec more on delay shortly … 1 - 37 source R bps destination 321 L bits per packet R bps end-end delay = 2 L / R (assuming zero propagation delay) Introduction Packet Switching: queueing delay, loss A B R = 100 Mb/s^ C R = 1.5 Mb/s
queue of packets^ E waiting for output link 1 - 38
If arrival rate (in bits) to link exceeds transmission rate of link for a period of time: packets will queue, wait to be transmitted on link packets can be dropped (lost) if memory (buffer) fills up
Network Layer 4 - 39
router’s input to appropriate router output
destination route taken by packets routing algorithms routing algorithm local forwarding table header value output link 0100 0101 0111 1001 3 2 2 1 1 3 2 dest address in arriving packet’s header Introduction
In diagram, each link has four circuits. call gets 2nd^ circuit in top link and 1st^ circuit in right link. dedicated resources: no sharing circuit-like (guaranteed) performance circuit segment idle if not used by call (no sharing) Commonly used in traditional telephone networks 1 - 40
